Heat shock protein 90 (Hsp90) family (Hsp90)

The heat shock protein 90 family comprises highly conserved molecular chaperones critical for the folding, stabilization, and activation of a wide range of client proteins, including many involved in signal transduction, proliferation, and cell survival. Hsp90α and Hsp90β are cytoplasmic isoforms, with Hsp90α being inducible under stress and Hsp90β constitutively expressed under normal conditions[4][5][7]. Grp94, localized to the endoplasmic reticulum, specializes in folding secretory and membrane proteins and modulating immune responses[5]. These chaperones use an ATP-dependent mechanism, cycling between open and closed conformations to facilitate structural maturation of client proteins[1][2]. Because many of their clients are involved in oncogenic signaling, inflammation, or neuroprotection, Hsp90 proteins are validated drug targets—however, pan-inhibition faces toxicity challenges, prompting new efforts for isoform-selective pharmacology[4][5][7].

Other names

HSP90AA1Heat shock 90 kDa protein 1, inducible formHSP90AB1Heat shock 90 kDa protein 1, beta isoform, constitutive formHSP90B1glucose-regulated protein 94gp96endoplasmin

ATPase inhibition (disrupts Hsp90 chaperone cycle, leading to proteasomal degradation of client proteins); Disruption of client oncoprotein folding and stability (promotes apoptosis in cancer cells); Inhibition of inflammatory mediator production and immune cell signaling (noted with isoform-selective inhibition); Isoform-selective inhibition to reduce off-target toxicity.